Patent US3180360A successfully refreshed from Google Patents.
US3662255A
Expired / Lapsed
US
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Apparatus for locating concealed or buried metal bodies and a stable inductor usable in such detectors
Assignee: Individual
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Filing: 1970-04-13
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Granted: 1972-05-09
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Expires: 1990-04-13
Abstract
Abstract A metal detector for locating metal bodies buried in the ground or embedded in other structures having a probe assembly which is movable parallel to the surface of the earth or such structure and whose inductance varies as the inductor assembly is moved into the proximity of such concealed object, the detector providing an output signal whose frequency varies in accordance with the inductance of the probe assembly, wherein the probe assembly includes large diameter and small diameter inductor assemblies selectively connectible in a frequency determining circuit of an oscillator and wherein the signal produced by the detector may be indicated visually by means of a meter, audibly by a speaker to which the output of the detector is transmitted, or by neon bulbs mounted on the inductor assemblies which light up with a frequency which varies in accordance with the frequency of the output of the detector. A stable inductor assembly usable in detectors of the type described and having an inductor coil formed of a coaxial cable whose inner conductor is connected in the frequency determining circuit of an oscillator and whose outer coaxial conductor is grounded to form a partial Faraday shield between the inner conductor and a Faraday shield mounted exteriorly of the coil.
Inventors
- 👤 Charles L Garrett
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 12:10
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/15
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
108 words
A circular inductor assembly for a metal detector including: a coaxial cable having an inner control conductor, an outer conductor coaxial with and about said inner conductor, insulation means between said inner and outer conductors and about said outer conductor, said cable being disposed in a circular coil having a plurality of turns; a conductive shield disposed about the bottom portion of said coil; casing means about and enclosing said coil and said shield; and means for connecting one end of said inner conductor, said outer conductor and said shield to an electric ground and for connecting the other end of said inner conductor to an electric circuit.
Claim 2
Dependent Claim
108 words
A circular inductor assembly for a metal detector including: a coaxial cable having an inner control conductor, an outer conductor coaxial with and about said inner conductor, insulation means between said inner and outer conductors and about said outer conductor, said cable being disposed in a circular coil having a plurality of turns; a conductive shield disposed about the bottom portion of said coil; casing means about and enclosing said coil and said shield; and means for connecting one end of said inner conductor, said outer conductor and said shield to an electric ground and for connecting the other end of said inner conductor to an electric circuit.
Claim 3
Dependent Claim
36 words
The inductor assembly of claim 1, wherein said outer conductor and said shield constitute open electric paths, said connecting means being connected to said outer conductor and said shield at the midpoints of said electric paths.
Claim 4
Dependent Claim
52 words
The inductor assembly of claim 1, wherein said outer conductor comprises a pair of sections of equal lengths, adjacent ends of said sections being spaced from one another, said means for connecting said outer conductor to an electric ground being connected to the ends of said sections remote from said adjacent ends.
Claim 5
Dependent Claim
28 words
The assembly of claim 3, wherein said shield constitutes an open electric path, said connecting means being connected to said shield at the midpoint of its elecTric path.
Claim 6
Dependent Claim
48 words
The inductor assembly of claim 1, and a plurality of electric light means mounted adjacent said inductor assembly, and means for connecting said light means to an input circuit for causing said light means to flash in accordance with the frequency of the voltage of said input circuit.
Claim 7
Dependent Claim
199 words
A detector including: a first oscillator means for providing an output having a stable reference frequency; a second oscillator having a frequency determining circuit for varying the frequency of the output of said second oscillator; comparator means operatively associated with said oscillators for providing an output signal whose frequency varies in accordance with the difference between the frequencies of the outputs of said oscillator; and a circular inductor assembly comprising a coaxial cable having an inner central conductor, an outer conductor coaxial with and about said inner conductor, and insulation means between said inner and outer conductors and about said outer conductor, said cable being disposed in a circular coil having a plurality of turns; a conductive shield disposed about the bottom portion of said coil; casing means about and enclosing said coil and said shield; means for connecting one end of said inner conductor, said outer conductor and said shield to an electric ground of said second oscillator, and means for connecting the other end of said inner conductor to said frequency determining circuit of said second oscillator, the frequency of the output of said second oscillator varying in accordance with the effective inductance of said inductor assembly.
Claim 8
Dependent Claim
199 words
A detector including: a first oscillator means for providing an output having a stable reference frequency; a second oscillator having a frequency determining circuit for varying the frequency of the output of said second oscillator; comparator means operatively associated with said oscillators for providing an output signal whose frequency varies in accordance with the difference between the frequencies of the outputs of said oscillator; and a circular inductor assembly comprising a coaxial cable having an inner central conductor, an outer conductor coaxial with and about said inner conductor, and insulation means between said inner and outer conductors and about said outer conductor, said cable being disposed in a circular coil having a plurality of turns; a conductive shield disposed about the bottom portion of said coil; casing means about and enclosing said coil and said shield; means for connecting one end of said inner conductor, said outer conductor and said shield to an electric ground of said second oscillator, and means for connecting the other end of said inner conductor to said frequency determining circuit of said second oscillator, the frequency of the output of said second oscillator varying in accordance with the effective inductance of said inductor assembly.
Claim 9
Dependent Claim
35 words
The detector of claim 6, wherein said outer conductor and said shield constitute open electric paths, said connecting means being connected to said outer conductor and said shield at the midpoints of said electric paths.
Claim 10
Dependent Claim
33 words
The detector of claim 7, and indicator means responsive to the output of said comparator means for providing a signal which varies in accordance with the frequency of the output of said means.
Claim 11
Dependent Claim
27 words
The detector of claim 8 wherein said indicator means comprise electric light means which flash in accordance with the frequency of the output of said comparator means.
Claim 12
Dependent Claim
193 words
A metal detector including: first and second circular inductor assemblies of different diameters and lying in a common plane, each inductor assembly comprising a coaxial cable having an inner conductor, an outer conductor coaxial with and about said inner conductor, insulation means between said inner and said outer conductors and about said outer conductors, said cable being disposed in a circular coil having a plurality of turns, and a conductive shield disposed about the bottom portion of said coil; casing means about and enclosing said coils and said shields of said inductor assemblies; a first oscillator having an output of a stable reference frequency; a second oscillator having a frequency determining circuit; means for selectively connecting one end of said inner conductor of each of said inductor assemblies to said frequency determining circuit, the frequency of the output of said second oscillator varying in accordance with the effective impedance of the inductor assembly whose inner conductor is connected to said frequency determining circuit; and comparing means operatively associated with said oscillators for providing an electric output signal which varies in accordance with the difference in the frequencies of the outputs of said oscillators.
Claim 13
Dependent Claim
193 words
A metal detector including: first and second circular inductor assemblies of different diameters and lying in a common plane, each inductor assembly comprising a coaxial cable having an inner conductor, an outer conductor coaxial with and about said inner conductor, insulation means between said inner and said outer conductors and about said outer conductors, said cable being disposed in a circular coil having a plurality of turns, and a conductive shield disposed about the bottom portion of said coil; casing means about and enclosing said coils and said shields of said inductor assemblies; a first oscillator having an output of a stable reference frequency; a second oscillator having a frequency determining circuit; means for selectively connecting one end of said inner conductor of each of said inductor assemblies to said frequency determining circuit, the frequency of the output of said second oscillator varying in accordance with the effective impedance of the inductor assembly whose inner conductor is connected to said frequency determining circuit; and comparing means operatively associated with said oscillators for providing an electric output signal which varies in accordance with the difference in the frequencies of the outputs of said oscillators.
Claim 14
Dependent Claim
21 words
The metal detector of claim 10 wherein one of said inductor assemblies is disposed within the other of said inductor assemblies.
Claim 15
Dependent Claim
40 words
The metal detector of claim 11 and indicating means operatively associated with said comparator means for providing a signal perceivable by an operator of the detector which varies in accordance with the frequency of the output of said comparator means.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-09 | 1975-11-08 | 1976-05-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-09 | 1979-11-08 | 1980-05-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-09 | 1983-11-08 | 1984-05-09 | $7700.00 | Window Closed / Lapsed |